feat(router): add support for payment_type field in payment intent

[vspecky]

Type of Change

• Bugfix
• New feature
• Enhancement
• Refactoring
• Dependency updates
• Documentation
• CI/CD

Description

This PR adds a new payment_type column in the payment_intent table, the value of which is inferred during payment creation, and is also included in the response of the list payment methods call.

Additional Changes

• This PR modifies the API contract
• This PR modifies the database schema
• This PR modifies application configuration/environment variables

Motivation and Context

The payment_type field will be detrimental in deciding the right mandate flow. Certain merchants may want to just set up the mandate without debiting any amount, whereas some merchants may want to debit some amount as part of the setup. This distinction is done based on the payment_type.

How did you test it?

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code
• I added unit tests for my changes where possible
• I added a CHANGELOG entry if applicable